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SIP Myths

On this page, we try to present some of the myths surrounding ▲SIP and provide the real truth. We hope that this might help in your fairly judging the technology and deciding whether this is the right solution for you, either short-term or long-term.

1. SIP is an Emerging Protocol

Look at the top of this page to see just how old SIP is. How long does it take for a technology to emerge. Planets emerge. Stars emerge. Should it take so long for a ▲VoIP technology to emerge?

SIP is hardly new and it has been updated and revised for years. SIP is really quite an old protocol, yet people continue to apply the word "emerging" to the technology. Even after all of these years, the capabilities that SIP delivers are not fantastic. Other protocols have far exceeded SIP's capabilities and, while it might be correct to say that it is emerging, one has to question whether it is worth waiting for it to finally emerge. Even while new capabilities are slowly added to SIP, problems are constantly discovered that need to be addressed. As such, what limited benefits it might deliver are offset by interoperability problems.

2. SIP is Simple

This is false. Telephony, by its very nature, is not simple. In order to implement the most basic and practically useless call flow, sure it looks simple. However, if you want to actually create something useful, there is an inordinate amount of complexity involved. SIP was originally designed to simply make a "black phone" ring. From there, SIP was expanded and extended to allow for more general-purpose telephony. Further, it was discovered later that SIP over ▲UDP was not a very workable solution, so ▲TCP was recommended for most calls. To implement a basic SIP phone, one needs to support TCP and UDP, one needs to support most all of the features in RFC 3261 and many of the features from dozens of other RFCs. Further, because there are reliability issues with transmitting messages, the concept of reliable provisional responses was introduced and is necessary to ensure proper functionality. We could go on, but to say the least, SIP is hardly simple and is, in many respects, more complex than more capable video conferencing standards like ▲H.323.

The charts at VoIP RFC Watch are useful.

3. SIP Can Do Many Things that Were Never Possible Before

There is nothing that SIP can do that other ▲IP-based communication protocols cannot do. In fact, much of the functionality that SIP has been trying to deliver to the market for years was delivered by competitors like Skype in a very short time. Further, SIP is still very weak in terms of basic audio/visual communications, something at which H.323 excels. SIP has the potential to enable other forms of communication, of course, and instant messaging is one. But, it is important to note that H.323, Skype, or anything else can also deliver those same capabilities. So, where is SIP's advantage here? It does not have one.

4. SIP Will Enable All Kinds of New Applications

SIP or any other IP-based system could enable a host of new applications. The fact is, though, that most implementations suffer with basic interoperability issues. Further, how much work is it to add a simple application to a SIP phone? How much work is there in adding ▲instant messaging support? How much work is there in adding electronic whiteboard functionality? This list can go on forever. It is actually quite difficult to extend SIP to add new functionality. Once you decide to add new functionality to SIP, you must update the entire SIP software application. By the very design of SIP, it is note easily extensible in terms of adding new functionality. Further, if you are an independent software vendor and you wish to add new functionality to another company's SIP product, it is a monumental task, if not an impossible one.

The problem is further complicated by the fact that SIP proxies, softswitches, ▲session border controllers and other devices in the network would likely not support any new functionality without also being upgraded. By SIP's very design, it is not very easy to extend and enhance the protocol to supports new kinds of applications.